1. Field of the Invention
The present invention relates to an .alpha.-olefin polymerization catalyst and a process for producing an .alpha.-olefin polymer. Particularly, the present invention relates to an .alpha.-olefin polymerization catalyst giving a highly stereoregular .alpha.-olefin polymer of high bulk density containing an extremely little catalyst residue and amorphous polymer and having excellent mechanical properties and processability, and having an extremely high catalytic activity per a solid catalyst and per a transition metal atom, and a process for producing a highly stereoregular .alpha.-olefin polymer of high bulk density with said catalyst.
2. Prior Art
As a process for producing the polymer of .alpha.-olefin such as propylene, butene-1 or the like, it is well known that the so-called Ziegler-Natta catalyst comprising the transition metal compound of the 4th to 6th Groups and the organometallic compound of the 1st, 2nd and 13th Groups in the Periodic Table is used.
In the production of .alpha.-olefin polymers, an amorphous polymer is formed as by-product in addition to a highly stereoregular .alpha.-olefin polymer having a high value in industrial application. This amorphous polymer has little value in industrial application and effects largely a bad influence on mechanical properties, when an .alpha.-olefin polymer is molded to a molded article, a film, a fiber and other fabricated goods to be used. The formation of the amorphous polymer causes the loss of a raw material monomer and at the same time, an apparatus for removing an amorphous polymer becomes necessary to cause an extremely large disadvantage from an industrial viewpoint. Therefore, it is necessary that a catalyst for producing an .alpha.-olefin polymer forms no amorphous polymer or forms rarely little.
In the .alpha.-olefin polymer obtained, a residue of catalyst comprising a transition metal compound and an organometallic compound remains. As this catalyst residue causes problems in the various points such as stability, processability and the like of the .alpha.-olefin polymer, an apparatus for removing the catalyst residue thereby stabilizing the polymer becomes necessary. As this defect can be improved by increase a catalyst activity represented by the weight of the .alpha.-olefin polymer produced per the unit weight of a catalyst, the above-mentioned apparatus for removing the catalyst residue becomes unnecessary and the reduction of the manufacturing cost of .alpha.-olefin polymer also becomes possible.
It is known that highly stereoregular and highly active polymerization of .alpha.-olefin can be realized to a certain extent by using a Ti--Mg complex type solid catalyst obtained by reducing a tetra-valent titanium compound with an organomagnesium compound in the presence of an organosilicon compound and forming the magnesium-titanium eutectic mixture, in combination with the organoaluminum compound of a promotor and the organosilicon compound as a third component in polymerization. (Japanese Patent Publication (Examined) Nos. Hei 3-43283(1991), Hei 1-319508(1989))
In any case, a non-extraction and non-deashing process is in a possible level, but furthermore, a more improvement is desired. In the concrete, in order to produce an .alpha.-olefin polymer of high quality, the realization of further highly stereoregular polymerization without sacrificing a particle size distribution and the like is desired. Particularly, in a use such as a field for molding wherein it is desired to make a polymer be in high rigidity, a highly stereoregular polymer brings directly out the quality of a high rigidity, and therefore, the appearance of a catalyst having a further highly stereoregular polymerizability, a high bulk density and a narrow particle size distribution is acutely desired.